1. Field of the Invention
The present invention relates to a hollow golf club head.
2. Description of the Related Art
Performances desired for hollow golf club heads include hitting sound, resilience, moment of inertia, ease of setting, and the like. Hitting sound of the hollow golf club head is loud. With respect to the hollow golf club heads, improvement of hitting sound has been desired. Clear hitting sound with high frequency is apt to be preferred. In addition, the hollow golf club head has a large volume. Large heads may be difficult in setting. Ease of setting correlates with the extent of setting stability. The term extent of setting stability means the extent of stability of the head in addressing. The heads with inferior setting stability are not stable in addressing.
Proposals for improvement of the hitting sound have been made. Japanese Unexamined Patent Application Publication No. Hei 10-33724 discloses a head provided with a Y-shaped metal inside the head for improving the hitting sound. Japanese Unexamined Patent Application Publication No. 2002-126136 discloses a head provided with a linear protrusion inside the head for improving the hitting sound. Japanese Unexamined Patent Application Publication No. 2004-49559 discloses a head with a devised sole for improving the hitting sound. Japanese Unexamined Patent Application Publication No. 2004-49733 discloses a head with a devised thickness of the sole for improving the hitting sound. United States patent corresponding to Japanese Unexamined Patent Application Publication No. 2002-126136 is U.S. Pat. No. 6,645,087. United States patent corresponding to Japanese Unexamined Patent Application Publication No. 2004-49733 is U.S. Pat. No. 7,160,205.